勒

lè
  1. (literary) bridle; halter; headstall
  2. to rein in
  3. to compel; to force
  4. (literary) to carve; to engrave
  5. (literary) to command; to lead (an army etc)
  6. (physics) lux (abbr. for 勒克斯 lèkèsī)

CEDICT

literary physics

Homographs

勒 lēi
  1. to strap tightly
  2. to bind